Larvicultura do pirarucu em sistema de bioflocos

Abstract

Arapaima is considered the largest carnivorous species of Amazon and can reach up to 200 kg in the natural environment. Its high market value is due to its fast growth, the peculiar taste of its flesh and the possibilities of use of its byproducts. One of the main challenges of the Arapaima farming is to offer its early stages because there is a high rate of mortality during the larval phase. In this phase, the larvae are usually in the ponds together with the breeding fish, when they are susceptible to parasites, predators and lack of live food. As an alternative, the intensive larviculture allows the control of the environment, creating appropriate conditions for the larvae development. The biofloc technology (BFT) fits this possibility because it provides a better control of the quality of water and pathogens, and the biofloc could be an additional source of food. The objective of this work is to evaluate the performance of the Arapaima larvae reared in BFT. The experimental design was completely randomized with two treatments, a system with clear water (AC) as control and a system of biofloc (BFT), composed of five replication tanks. Arapaima larvae were (0.778 ± 0.02 g and 4.84 ± 0.11 cm) were housed in PVC tanks (20 L; 25 fish per tank). Initially and at the end of the experiment, water were collected and five fish from each treatment were euthanized for microbiological analyzes of the gastrointestinal tract. At the end of the experiment, the water of the BFT was filtered for determination of the proximate composition of the biofloc. There was no significant difference between the performance variables in both treatments; such result was attributed to the inadequate ingestion of food due to the high need of airing for the biofloc floating, causing stress and possibly altering the immunity of the larvae, making them susceptible to pathogenic bacteria; in addition to the elevated levels of nitrogenous compounds, due to the high excretion of the larvae, becoming toxic to the fish. The BFT presented the greatest diversity of bacteria, being identified the genus Aeromonas, Bacillus, Citrobacter, Enterobacter, Hafnia, Klebsiella, Morganella, Proteus, Pseudomonas, Salmonella, Serratia, Staphylococcus and Yersinia. The biofloc presented 41% of crude protein. Although BFT is an ecologically system for reducing water use and recycling effluents, adjustments are still needed, such as keeping the biofloc at low levels, so that its use is feasible for Arapaima larvicultura.